The circadian clocks in chlorophyte algae have been studied in two model organisms, Chlamydomonas reinhardtii and Ostreococcus tauri. These studies revealed that the chlorophyte clocks include some genes that are homologous to those of the angiosperm circadian clock. However, the genetic network architectures of the chlorophyte clocks are largely unknown, especially in C. reinhardtii. In this study, using C. reinhardtii as a model, we characterized RHYTHM OF CHLOROPLAST (ROC) 75, a clock gene encoding a putative GARP DNA-binding transcription factor similar to the clock proteins LUX ARRHYTHMO (LUX, also called PHYTOCLOCK 1 [PCL1]) and BROTHER OF LUX ARRHYTHMO (BOA, also called NOX) of the angiosperm Arabidopsis thaliana. We observed that ROC75 is a day/subjective day-phase-expressed nuclear-localized protein that associates with some night-phased clock genes and represses their expression. This repression may be essential for the gating of reaccumulation of the other clock-related GARP protein, ROC15, after its light-dependent degradation. The restoration of ROC75 function in an arrhythmic roc75 mutant under constant darkness leads to the resumption of circadian oscillation from the subjective dawn, suggesting that the ROC75 restoration acts as a morning cue for the C. reinhardtii clock. Our study reveals a part of the genetic network of C. reinhardtii clock that could be considerably different from that of A. thaliana.

在绿藻藻类的生物钟已经研究了两种模式生物，莱茵衣藻和Ostreococcus金牛座。这些研究表明，叶绿素生物钟包括一些与被子植物生物钟生物钟基因同源的基因。但是，叶绿素钟的遗传网络结构在很大程度上尚不清楚，尤其是在C中。Reinhardtii。在这项研究中，使用Ç。reinhardtii作为模型，我们表征了叶绿体的节奏（ROC）75，一种编码假定的GARP DNA结合转录因子的时钟基因，类似于被子植物拟南芥的时钟蛋白LUX ARRHYTHMO（LUX，也称为PHYTOCLOCK 1 [PCL1]）和LUX ARRHYTHMO（BOA，也称为NOX）。我们观察到，ROC75是一种白天/主观的白天表达的核定位蛋白，与某些夜间阶段的时钟基因相关联并抑制其表达。这种抑制可能是门控其他依赖于时钟的GARP蛋白ROC15在光依赖降解后重新积累的必不可少的条件。ROC75功能在心律不齐的roc75中的恢复突变体在恒定的黑暗中导致主观黎明恢复昼夜节律振荡，这表明ROC75还原体是C的早晨提示。reinhardtii时钟。我们的研究揭示了C的遗传网络的一部分。reinhardtii时钟可能与A的时钟有很大不同。拟南芥。